/*
 * Copyright (C) 2008 by The Regents of the University of California
 * Redistribution of this file is permitted under the terms of the GNU
 * Public License (GPL).
 *
 * @author Junghoo "John" Cho <cho AT cs.ucla.edu>
 * @date 3/24/2008
 */
 
#include "BTreeIndex.h"
#include "BTreeNode.h"

using namespace std;

/*
 * BTreeIndex constructor
 */
BTreeIndex::BTreeIndex()
{
    rootPid = -1;
	treeheight = 0;
}

/*
 * Open the index file in read or write mode.
 * Under 'w' mode, the index file should be created if it does not exist.
 * @param indexname[IN] the name of the index file
 * @param mode[IN] 'r' for read, 'w' for write
 * @return error code. 0 if no error
 */
RC BTreeIndex::open(const string& indexname, char mode)
{
	this->mode = mode;
	if(pf.open(indexname, mode) != 0) {
		return RC_FILE_OPEN_FAILED;
	}
	if(mode == 'w') {
		return 0;
	}
	char buffer[PageFile::PAGE_SIZE];
	if(pf.read(0, buffer) != 0) {
		return RC_FILE_READ_FAILED;
	}
	char* iterator = &(buffer[0]);
	memcpy(&rootPid, &(buffer[0]), sizeof(PageId));
	iterator += sizeof(PageId);
	memcpy(&treeheight, iterator, sizeof(int));
    return 0;
}

/*
 * Close the index file.
 * @return error code. 0 if no error
 */
RC BTreeIndex::close()
{
	char buffer[PageFile::PAGE_SIZE];
	char* iterator = &(buffer[0]);
	if( mode == 'w' ) {
		memset(&(buffer[0]), 0, PageFile::PAGE_SIZE);
		memcpy(&(buffer[0]), &rootPid, sizeof(PageId));
		iterator += sizeof(PageId);
		memcpy(iterator, &treeheight, sizeof(PageId));
		if( pf.write(0, buffer) != 0) {
			return RC_FILE_WRITE_FAILED;
		}
	}
    return pf.close();
}

/*
 * Insert (key, RecordId) pair to the index.
 * @param key[IN] the key for the value inserted into the index
 * @param rid[IN] the RecordId for the record being inserted into the index
 * @return error code. 0 if no error
 */
RC BTreeIndex::insert(int key, const RecordId& rid)
{
	IndexCursor ic;

	PageId pid;
	PageId oldpid;
	BTNonLeafNode node;
	BTLeafNode leaf;
	BTNonLeafNode sib;
	int midkey;

	locate(key, ic);

	if(treeheight == 1) {
	  leaf.read(ic.pid, pf);
	  if( leaf.insert(key, rid) == 0) 
		leaf.write(ic.pid, pf);
		return 0;
	}
	
	if( leaf.read(ic.pid, pf) != 0) {
		return RC_FILE_READ_FAILED;
	}
	if(leaf.insert(key, rid) != 0) {
		BTLeafNode sibling;
		int sibkey;
		leaf.insertAndSplit(key, rid, sibling, sibkey);
		sibling.setNextNodePtr(leaf.getNextNodePtr());
		leaf.setNextNodePtr(pf.endPid());
		if( leaf.write(ic.pid, pf) != 0) {
			return RC_FILE_WRITE_FAILED;
		}
		if( sibling.write(pf.endPid(), pf) != 0) {
			return RC_FILE_WRITE_FAILED;
		}
		if(treeheight == 1) {
			BTNonLeafNode root;
			root.initializeRoot(ic.pid, sibkey, (pf.endPid() - 1));
			if(root.write(pf.endPid(), pf) != 0) {
				return RC_FILE_WRITE_FAILED;
			}
			rootPid = pf.endPid() - 1;
			treeheight++;
			return 0;
		}
		int i = 0;
		do {
			oldpid = pid;
			pidlist.pop_back();
			if( node.read(pid, pf) != 0) {
				return RC_FILE_READ_FAILED;
			}
			if(i == 0) {
				if(node.insert(sibkey, pf.endPid()-1) == 0) {
					if(node.write(pid, pf) != 0) {
						return RC_FILE_WRITE_FAILED;
					}
					break;
				} else {
					node.insertAndSplit(sibkey, ic.pid, sib, midkey);
					sib.write(pf.endPid(), pf);
					if(node.write(pid, pf) != 0) {
						return RC_FILE_WRITE_FAILED;
					}
				}
			} else {
				if(node.insert(midkey, oldpid) == 0) {
					if( node.write(pid, pf) != 0) {
						return RC_FILE_WRITE_FAILED;
					}
					break;
				} else {
					node.insertAndSplit(midkey, oldpid, sib, midkey);
					sib.write(pf.endPid(), pf);
					if(pid == rootPid) {
						BTNonLeafNode root;
						root.initializeRoot(pid, midkey, pf.endPid()-1);
						if(root.write(pf.endPid(), pf) != 0) {
							return RC_FILE_WRITE_FAILED;
						}
						rootPid = pf.endPid() - 1;
						treeheight++;
					}
					if( node.write(pid, pf) != 0) {
						return RC_FILE_WRITE_FAILED;
					}
					break;
				}
			}
			i++;
		} while(pid != rootPid);
	}
	if(leaf.write(ic.pid, pf) != 0) {
		return RC_FILE_WRITE_FAILED;
	}
    return 0;
}

/*
 * Find the leaf-node index entry whose key value is larger than or 
 * equal to searchKey, and output the location of the entry in IndexCursor.
 * IndexCursor is a "pointer" to a B+tree leaf-node entry consisting of
 * the PageId of the node and the SlotID of the index entry.
 * Note that, for range queries, we need to scan the B+tree leaf nodes.
 * For example, if the query is "key > 1000", we should scan the leaf
 * nodes starting with the key value 1000. For this reason,
 * it is better to return the location of the leaf node entry 
 * for a given searchKey, instead of returning the RecordId
 * associated with the searchKey directly.
 * Once the location of the index entry is identified and returned 
 * from this function, you should call readForward() to retrieve the
 * actual (key, rid) pair from the index.
 * @param key[IN] the key to find.
 * @param cursor[OUT] the cursor pointing to the first index entry
 *                    with the key value.
 * @return error code. 0 if no error.
 */
RC BTreeIndex::locate(int searchKey, IndexCursor& cursor)
{
	switch(treeheight) {
		case 0:{
			cursor.pid = 1;
			cursor.eid = 0;
			treeheight++;
			rootPid = 1;
		break;}
		case 1:
			{BTLeafNode root;
			int eid;
			if(root.read(rootPid, pf) != 0) {
				return RC_FILE_READ_FAILED;
			}
			if(root.locate(searchKey, eid) != 0) {
				return RC_NO_SUCH_RECORD;
			}
			cursor.pid = rootPid;
			cursor.eid = eid;
		break;}
		default:{
			BTNonLeafNode node;
			if(node.read(rootPid, pf) != 0) {
				return RC_FILE_READ_FAILED;
			}
			int level = 1;
			while(level < treeheight) {
				if(level == 1) {
					pidlist.push_back(rootPid);
				} else {
					pidlist.push_back(nextPid);
				}	
				if(node.locateChildPtr(searchKey, nextPid) != 0) {
					return RC_NO_SUCH_RECORD;
				}
				if(node.read(nextPid, pf) != 0) {
					return RC_FILE_READ_FAILED;
				}
				level++;
			}
			cursor.pid = nextPid;
			cursor.eid = 0;
		break;}
	}
    return 0;
}

/*
 * Read the (key, rid) pair at the location specified by the index cursor,
 * and move foward the cursor to the next entry.
 * @param cursor[IN/OUT] the cursor pointing to an leaf-node index entry in the b+tree
 * @param key[OUT] the key stored at the index cursor location.
 * @param rid[OUT] the RecordId stored at the index cursor location.
 * @return error code. 0 if no error
 */
RC BTreeIndex::readForward(IndexCursor& cursor, int& key, RecordId& rid)
{
	//to be implemented in Part C
	BTLeafNode node;
	if(node.read(cursor.pid, pf) != 0) {
		return RC_FILE_READ_FAILED;
	}

	if(node.readEntry(cursor.eid, key, rid) != 0) {
		return RC_INVALID_RID;
	}

	if (cursor.eid < node.getKeyCount() - 1) {
		cursor.eid++;
	} else {
		cursor.eid = 0;
		if(node.getNextNodePtr() == 0) {
			return RC_END_OF_TREE;
		}
		cursor.pid = node.getNextNodePtr();
	}	

    return 0;
}
